Streamer propagation in the atmosphere of Titan and other N2:CH4 mixtures compared to N2:O2 mixtures

Abstract

Streamers, thin, ionized plasma channels, form the early stages of lightning discharges. Here we approach the study of extraterrestrial lightning by studying the formation and propagation of streamer discharges in various nitrogen-methane and nitrogen-oxygen mixtures with levels of nitrogen from 20% to 98.4%. We present the friction force and breakdown fields Ek in various N2:O2 (Earth-like) and N2:CH4 (Titan-like) mixtures. The strength of the friction force is larger in N2:CH4 mixtures whereas the breakdown field in mixtures with methane is half as large as in mixtures with oxygen. We use a 2.5 dimensional Monte Carlo particle-in-cell code with cylindrical symmetry to simulate the development of electron avalanches from an initial electron-ion patch in ambient electric fields between 1.5Ek and 3Ek. We compare the electron density, the electric field, the front velocities as well as the occurrence of avalanche-to-streamer transition between mixtures with methane and with oxygen. Whereas we observe the formation of streamers in oxygen in all considered cases, we observe streamer inceptions in methane for small percentages of nitrogen or for large electric fields only. For large percentages of nitrogen or for small fields, ionization is not efficient enough to form a streamer channel within the length of the simulation domain. In oxygen, positive and negative streamers move faster for small percentages of nitrogen. In mixtures with methane, electron or streamer fronts move 10-100 times slower than in mixtures with oxygen; the higher the percentage of methane, the faster the fronts move.

arXiv comment34 pages, 11 figures, 1 table

References in corpus (14)

• Positive and negative streamers in ambient air: modeling evolution and velocities
• Photoionization in negative streamers: fast computations and two propagation modes
• Probing photo-ionization: simulations of positive streamers in varying N2:O2 mixtures
• Probing background ionization: Positive streamers with varying pulse repetition rate and with a radioactive admixture
• Deviations from the local field approximation in negative streamer heads
• Streamers, sprites, leaders, lightning: from micro- to macroscales
• Density models for streamer discharges: beyond cylindrical symmetry and homogeneous media
• Spatially hybrid computations for streamer discharges: II. Fully 3D simulations
• Sprite discharges on Venus and Jupiter-like planets: a laboratory investigation
• Lightning climatology of exoplanets and brown dwarfs guided by Solar System data
• Ionisation in atmospheres of brown dwarfs and extrasolar planets VI: Properties of large-scale discharge events
• The Allen Telescope Array Search for Electrostatic Discharges on Mars
• Is lightning a possible source of the radio emission on HAT-P-11b?
• Mesospheric optical signatures of possible lightning on Venus

Cited by in corpus (5)

• Isotopic constraints on lightning as a source of fixed nitrogen in Earth's early biosphere
• Neutral dissociation of methane by electron impact and a complete and consistent cross section set
• Understanding the atmospheric properties and chemical composition of the ultra-hot Jupiter HAT-P-7b: III. Changing ionisation and the emergence of an ionosphere
• Exploring terrestrial lightning parameterisations for exoplanets and brown dwarfs
• 3D particle simulations of positive air-methane streamers for combustion